Keeping motivation was the hardest part
The canopy was really the biggest problem, particularly the fiberglass layup. It ended up taking about 2 months for that, plus another month of prep on it. It looks perfect when done, but it took a bunch of time to do. The cowling can take a very long time as well, though it hangs pretty quickly.
The fuel tank took a very long time as well, you must be extra careful, though I think mine was overly cautious.
The most time consuming/careful-ness required bit was the wiring though. You lay every wire individually, and I ended up double and triple checking each connection.
331RV has probably been near-ready for flight since mid-december, but waiting on the painter took a while, and there was a bunch of stuff that was waiting on that. If you fly before paint,you'll be in better shape as far as that is concerned.
Avionics is pretty trivial when it comes right down to it, I think the whole kit went together in a less than a weekend. I had a bunch of problems with one of my AP servos (as well as having ot return the AP), so about 2 months were burned there.